Phase and amplitude modulation of light is usually generated by the electro-optic effect, where the index of refraction of a dielectric material is changed by applying a variable external electric field. Typically, a sinusoidal electric field with a fixed frequency is applied across a birefringent electro-optic crystal. This effect can be used to generate phase modulation, amplitude modulation, and/or polarization rotation/variation depending on the polarization state of the incident light and the orientation of the crystal. Current designs typically use one pair of electrodes per modulator material block to apply the electric field, as shown in FIG. 1. The modulator material is commonly made of a transparent, crystalline medium with electro-optic properties, which can be referred to as a modulator crystal. When multiple, e.g., 3, modulation frequencies are required, multiple, e.g., 3, modulators are currently used to provide the multiple frequencies.
Phase modulation of light is often generated by utilization of the electro-optic effect, where the index of refraction of a dielectric material is changed by applying a variable external electric field, typically a sinusoidal voltage at a fixed frequency, applied across the crystal, perpendicular to the direction of travel of the light. The electro-optic effect can also be used to generate amplitude modulation, and/or to rotate the polarization of the incident light, by adjusting the polarization state of the incident light and the orientation of the crystal. The generation of amplitude modulation, when certain orientations of the polarization state of the incident light and the orientation of the crystal occur, makes it hard to achieve pure phase modulation without spurious, unwanted, amplitude modulation or polarization rotation. The modulator material is usually made of a transparent, crystalline medium with electro-optic properties, which can be referred to as a modulator crystal. Current phase modulator designs use crystal front faces that are parallel, as shown in FIG. 1. In the design shown in FIG. 1, both polarizations (x and z) of the incoming beam remain superimposed in the outgoing beam.